1. Field of the Invention
The present invention is directed to a method for fabricating composite structures. Particularly, the present invention relates to a method for forming composite primary and secondary structures employing a continuous net-shape material supply in a continuous press forming process and a pultrusion fabrication process at a low-cost, moderate-to-high production rate.
2. Description of the Related Art
There are numerous methods for the fabrication of composite structures, including, but not limited to, thermoforming polymeric matrices and autoclave processing. However, all are either labor intensive, more costly than using purely metallic materials, not applicable to moderate-to-high volume applications, or do not result in high structurally-efficient structures. The prior art processes are generally batch oriented, such as those employed for autoclave cured structures.
Fabrication of complex non-uniform structural members is a labor intensive process typically consisting of cutting and darting fabric to facilitate the conformance of planar materials to non-planar geometries. The cost of the resulting structures is high, requires considerable time to produce and the process is prone to errors. Even utilizing automated material placement systems which are known in the art, such as advanced tow placement, the time required to produce a structure, the cost and the part quality is less than optimal.
There are pultrusion processing methods known in the art in which heat-cured, pultruded, composite structures can be produced at moderate-to-high production rates. However, in these processing methods a resin system is employed that sacrifices structural performance for rapid processing. Furthermore, conventional pultruded structures are generally unsuitable for primary structural applications due to their less than optimal structural performance. Lower structural performance is due to non-optimal fiber orientations in the fabric and the necessity of using rapid curing resins that have non-optimal structural performance.